1. Field of the Invention
The present invention relates to a three-dimensional ultrasonic diagnostic apparatus. More particularly, the present invention relates to an image memory technique for easily achieving many varieties of three-dimensional image analyses under arbitrary display conditions for volume data obtained in the past, by storing an obtained volume data in a loop memory in time series in a real-time three-dimensional ultrasonic diagnostic apparatus for carrying out an acquisition and display of the volume data in real time.
2. Description of the Background Art
A two-dimensional ultrasonic diagnostic apparatus conventionally utilized employs a system for displaying a tomographic image obtained by scanning one tomographic plane by an ultrasonic wave beam. In the mean time, in recent years, there have been carried out various trials of three-dimensional ultrasonic diagnosis for obtaining three-dimensional image data (that is, volume data) by acquiring diagnostic images while moving an ultrasonic probe that is an ultrasonic transceiver in a three-dimensional ultrasonic diagnostic apparatus. Thus, there has been placed a large expectation in a potential of a new diagnosis based on a three-dimensional image in this three-dimensional ultrasonic diagnostic apparatus. More particularly, researches have been progressed which is concerning the use of a manually or mechanically moving a convex probe or a linear-arrayed probe for abdomen or a multi-plane probe through esophagus having a function of rotating an electronic sector probe.
Particularly, there have recently been progressed researches and developments on a real-time three-dimensional ultrasonic diagnostic apparatus for acquiring and displaying three-dimensional information in real time, by electronically carrying out a three-dimensional scanning by ultrasonic waves at high speed. In other words, this real-time three-dimensional ultrasonic diagnostic apparatus is an apparatus for sequentially displaying volume data that is three-dimensional image data acquired.
The above-described three-dimensional ultrasonic diagnostic apparatus, however, has the following problems.
This real-time three-dimensional ultrasonic diagnostic apparatus is still at a research stage, and fundamentals including a detailed method of achieving this apparatus or utilizing the apparatus have not yet been established.
According to the above-described two-dimensional ultrasonic diagnostic apparatus, as tomographic image data acquired by ultrasonic waves is simply displayed as a two-dimensional image, the tomographic image displayed and the acquired data basically correspond to each other at 1 to 1. Therefore, by merely storing the acquired image data itself on the image memory, it is easy to analyze the past data of image displayed in the past, by displaying of this past data again.
In this conventional two-dimensional ultrasonic diagnostic apparatus, the past image is an image data itself acquired in the past. For example, although there has been a technique for separately storing a plurality of kinds of images such as B mode images, Doppler images like CFM, M mode images, etc., these kinds of images are basically two-dimensional image data respectively. Therefore, there has never been a case of displaying images quite different from the images displayed in the past.
As a technique that can be used for storing the above-described past record of image data, there is available a cine-memory replay technique. This cine-memory is a loop-structured memory (loop memory) for storing data arranged in time array by sequentially updating the data at prescribed time intervals. This technique is disclosed in, for example, Japanese Patent Application Laid-open Publication No. Hei 3-210247.
On the other hand, according to the above-described three-dimensional ultrasonic diagnostic apparatus, it is not possible to display all the acquired three-dimensional image data (hereinafter to be referred to as volume data) on an image display unit (a cathode-ray tube, CRT). Therefore, it is necessary to image-process these volume data and display the processed result on a two-dimensional CRT as a three-dimensional display image. In other words, as compared with the two-dimensional ultrasonic diagnostic apparatus, the conventional three-dimensional ultrasonic diagnostic apparatus, particularly the real-time three-dimensional ultrasonic diagnostic apparatus for scanning ultrasonic image information three-dimensionally at high speed as not an acquisition of tomogpraphic images but as one volume data, and displaying the scanned result by sequentially processing the images, has a characteristic that the three-dimensional image data acquired by ultrasonic waves does not correspond to the displayed three-dimensional image data at 1 to 1.
Therefore, the above-described three-dimensional ultrasonic diagnostic apparatus has a problem that it is possible to display only limited three-dimensional data when only the displayed three-dimensional image data is used as the past image. The above-described memory for storing only the displayed image data has not been sufficient for a three-dimensional ultrasonic system.
Further, generally, at the time of carrying out an ultrasonic diagnosis, an image is displayed by always changing display conditions of the image in order to perform an optimum analysis of the image displayed.
Therefore, particularly in the case of observing a moving tissue such as a blood stream of a subject (that is, human body under examination), or in the case of observing a display image by moving it, the conventional three-dimensional ultrasonic diagnostic apparatus has a problem that it requires a frequent complex operation for adjusting display conditions each time an image displayed in the past is replayed, making it difficult to replay the past images.
In other words, a method of displaying a three-dimensional image with respect to three-dimensional image data is theoretically limitless. It has, therefore, been required to obtain a new technique for achieving a function of replaying a past image from the viewpoint of display conditions of identifying an angle and conditions from which an object to be diagnosed is observed as a three-dimensional image.
The present invention has been made to solve the above-described problems of the conventional technique. It is an object of the present invention to provide a three-dimensional ultrasonic diagnostic apparatus capable of displaying past three-dimensional display images retroactively to a prescribed past time, by keeping a record of volume data in a memory system of a loop memory (cine-memory) structure that stores data of time- series array by sequentially updating the data at prescribed time intervals.
Further, it is another object of the present invention to achieve a replay of a past three-dimensional display image can be achieved in an easy operation, by storing in the loop memory display conditions of the three-dimensional display image formed from the stored volume data. It may be so structured that a display condition of the past three-dimensional display image can be arbitrarily selected according to the need of desired analysis, from among a display condition based on the past display and a currently-set display condition.
Therefore, it is possible to carry out in an easy operation various three-dimensional image analyses retroactively to the past images based on the past volume data record. Furthermore, it is possible to carry out a three-dimensional image analysis at high speed and in high precision.
According to one aspect of the present invention, as shown in FIG. 1, there is provided an ultrasonic diagnostic apparatus, comprising:
a three-dimensional scanner (1, 2, 3) for carrying out a three-dimensional scanning by ultrasonic waves; a three-dimensional image data former 4 for forming three-dimensional image data based on scanning data obtained from the three-dimensional scanner; a three-dimensional image data memory 5 for storing in time series a plurality of pieces of three-dimensional image data formed by the three-dimensional image data former; a memory controller 6 for controlling write and read of the three-dimensional image data into or from the three-dimensional image data memory; and a display image former for forming a display image based on three-dimensional image data read out from the three-dimensional image data memory by the memory controller, and for displaying the formed display image on a display unit.
According to another aspect of the present invention, as shown in FIG. 2, there is provided an ultrasonic diagnostic apparatus, comprising:
a three-dimensional scanner (1, 2, 3) for carrying out a three-dimensional scanning by ultrasonic waves; a three-dimensional image data former 4 for forming three-dimensional image data based on scanning data obtained from the three-dimensional scanner; a three-dimensional image data memory 5 for storing in time series a plurality of pieces of three-dimensional image data formed by the three-dimensional image data former; a display condition data memory 10 for storing in time series a plurality of pieces of display condition data for forming the three-dimensional display image, the display condition data being corresponding to each of the tree-dimensional image data; a memory controller 62 for controlling write and read of the three-dimensional image data and the display condition data into or from the three-dimensional image data memory and the display condition data memory; and a display image former 7 for forming a display image based on three-dimensional image data read out from the three-dimensional image data memory and display condition data read out from the display condition data memory by the memory controller, and for displaying the formed display image on a display unit.
The apparatus shown in FIG. 2 may further comprise a display condition selector for selecting either the display condition data used in the past for forming a three-dimensional display image based on the three-dimensional image data or currently-set display condition data, according to a user""s instruction; wherein, the display image former forms a display image based on the read-out three-dimensional image data, based on display condition data selected by the display condition selector.
The display condition information may include at least one of a direction of a probe to a subject, opacity, color information added to a Doppler image, and a threshold value for extracting an area of the subject.
The above-described apparatus may further comprise a display image memory 15 for storing in time series a plurality of the display images, the display image being corresponding to the three-dimensional image data, as shown in FIG. 3.
The above-described apparatus may further comprise, as shown in FIG. 5, a position data generator 31 for generating probe position data according to a position of the three-dimensional scanner; and a position data memory 32 for storing in time series the probe position data obtained from the position data generator with making the probe position data correspond to each of the three-dimensional image data stored in the three-dimensional image data memory.
In this case, the display image former 7 may be structured to form a display image of a wider range than that of each of the three-dimensional image data by connecting a plurality of pieces of three-dimensional image data stored in the three-dimensional image data memory, according to the probe position data.
Alternatively, the display image former 7 may be structured to form a display image with corrected image quality of each three-dimensional image data by combining a plurality of pieces of three-dimensional image data stored in the three-dimensional image data memory, according to the probe position data.
Alternatively, the display image former 7 may also be structured to calculate a relative position for indicating what portion of a subject a display image corresponds to, according to reference position data for indicating a position of the three-dimensional scanner set on the subject and the probe position data, and to display an indicator for indicating the relative position based on the calculated relative position together with the display image.
Other features and advantages of the present invention will become apparent from the following description taken in conjunction with the accompanying drawings.